The present invention relates generally to test stations for IC (integrated circuit) devices, and more particularly, to a system and method for auto automatically protecting the IC devices from EOS (electro over stress) damage due to occurrence of an undesired DC transient during testing of the IC devices at a test station.
During manufacture of IC (integrated circuit) devices, such IC devices are tested at various test stations for determining various performance characteristics of such IC devices. Referring to FIG. 1, one example of such a test station is a burn-in test station 100 for determining the burn-in life time of the IC devices, as known to one of ordinary skill in the art of integrated circuit manufacture. The burn-in life time is a measure of the time period for which an IC device operates properly when the IC device is heated up from room temperature to a raised temperature such as about 125xc2x0 Celsius or about 150xc2x0 Celsius, for example, as known to one of ordinary skill in the art of integrated circuit manufacture.
Referring to FIG. 1, the burn-in test station 100 includes a testing board 102 which is placed inside an oven 104 having a heating element 106 for heating up the temperature within the oven 104. The testing board 102 includes a plurality of sockets including a first socket 112, a second socket 114, a third socket 116, a fourth socket 118, a fifth socket 120, and a sixth socket 122. Each of the sockets 112, 114, 116, 118, 120, and 122 holds an IC device during the determination of the burn-in life time of the IC devices A burn-in test station typically has more numerous sockets but six sockets are shown in the testing board 102 of FIG. 1 for clarity of illustration.
A temperature controller 130 coupled to the heating element 106 controls the heating element to set the temperature within the oven such that the IC devices within the sockets 112, 114, 116, 118, 120, and 122 of the testing board 102 heat up from room temperature to a raised temperature such as about 125xc2x0 Celsius or about 150xc2x0 Celsius, for example.
With such heating up of the IC devices, a DC (direct current) voltage (Vcc) is applied from a power voltage supply 132 to some pins of the IC devices within the sockets 112, 114, 116, 118, 120, and 122 of the testing board 102. In addition, another DC (direct current) voltage (Vbb) is applied from a biasing voltage supply 134 to other pins of the IC devices within the sockets 112, 114, 116, 118, 120, and 122 of the testing board 102. The voltage from the power voltage supply 132 and the biasing voltage supply 134 are used for biasing the IC devices for proper operation of the IC devices, as known to one of ordinary skill in the art of electronics.
With such proper biasing of the IC devices within the sockets 112, 114, 116, 118, 120, and 122 of the testing board 102, driving signals such as clock signals for example are coupled from a signal driver source 136 to the IC devices, as known to one of ordinary skill in the art of electronics. With such heating of the IC devices to the predetermined raised temperature and with proper biasing of the IC devices, the driving signals are repeatedly applied on the IC devices to measure a time period during which the IC devices operate properly. Such a time period is the burn-in life time of the IC devices determined by the burn-in test station 100.
During such a testing procedure within the burn-in test station 100, a DC transient may occur at various components of the burn-in test station 100. As illustrated in FIG. 2, a DC transient 202 is a sudden rise in voltage signal with time. For example, the DC transient 202 may include a voltage increase of about 7 volts.
The DC transient 202 may occur at the node of the power voltage supply 132 that is coupled to the IC devices within the sockets 112, 114, 116, 118, 120, and 122 for providing the power voltage Vcc to the IC devices. In addition, the DC transient 202 may also occur at the node of the biasing voltage supply 134 that is coupled to the IC devices for providing the biasing voltage Vbb to the IC devices.
Furthermore, the DC transient 202 may also occur at a node of the signal driver source 136 for providing a driving signal to the IC devices. Additionally, the DC transient 202 may also occur at a node of the testing board 102. For example the testing board 102 typically has a ground plane, as known to one of ordinary skill in the art of electronics. The DC transient 202 may occur at such a ground node of the testing board 102.
The DC transient 202 may occur at any of such nodes because such nodes are coupled to the general power system of a room having the test station 100. When a surge of power is drawn within such a power system, such as when another equipment demanding high power is turned on within the room, the DC transient 202 may result at any of the nodes of the power voltage supply 132, the biasing voltage supply 134, the signal driver source 136, and the testing board 102 as described herein.
When the DC transient 202 has a sufficiently high amplitude and/or is of a sufficient duration of time such that the DC transient 202 contributes significant power to the IC devices within the sockets 112, 114, 116, 118, 120, and 122, the IC devices may be damaged due to EOS (electro over stress) failure of the IC devices, as known to one of ordinary skill in the art of integrated circuit manufacture. Such EOS failure may result in premature failure of the IC devices, and the burn-in time of such IC devices may no longer be determined with accuracy.
Thus, a mechanism is desired for automatically protecting the IC devices from EOS (electro over stress) damage due to an undesired DC transient that may occur at a test station such as the burn-in test station.
Accordingly, in a general aspect of the present invention, nodes of a test station are monitored to detect any undesired DC transient, and a computer controls the components of the test station to properly shut down the test station in a timely manner to automatically protect the IC devices from EOS (electro over stress) damage due to the undesired DC transient.
The test station for testing the IC devices includes a testing board for holding the IC devices during testing of the IC devices. Furthermore, the test station includes at least one voltage supply for biasing the IC devices during testing of the IC devices. In addition, the test station includes a signal driver source for providing driving signals coupled to the IC devices during testing of the IC devices.
In one aspect of the present invention, a system for protecting the IC devices from EOS damage due to the undesired DC transient includes a signal measuring unit that monitors for occurrence of an undesired DC transient at any of the at least one voltage supply, of the signal driver source, and of at least one node of the testing board. The system also includes a data processing unit and a data interface bus coupled between the signal measuring unit and the data processing unit. The signal measuring unit sends, to the data processing unit via the data interface bus, a signal of the undesired DC transient measured at any of the at least one voltage supply, of the signal driver source, and of at least one node of the testing board.
The data processing unit determines whether the signal of the undesired DC transient exceeds threshold characteristics. The data processing unit includes a digital I/O (input/output) controller for controlling components of the test station such that the test station shuts down in a proper sequence when the signal of the undesired DC transient exceeds the threshold characteristics. The threshold characteristics indicate the level of power that may be transferred to the IC devices by the DC transient.
The present invention may be used to particular advantage when the test station includes a temperature controller for setting a temperature within an oven having the IC devices therein for performing a burn-in test on the IC devices. In that case, the proper sequence of shutting down the test station upon detection of a sufficiently undesirable DC transient includes first controlling the temperature controller to reduce the temperature within the oven to about 10xc2x0 Celsius above room temperature from a raised temperature of about 125xc2x0 Celsius or about 150xc2x0 Celsius for example, then turning off the driving signals from the signal driver source, then turning off a biasing voltage supply Vbb, and then turning off a power voltage supply Vcc.
With such automatic shutting down of the test station in the proper sequence using data processing control such as computer control, the IC devices are protected from EOS damage from the undesired DC transient. Thus, the testing of the IC devices may resume after such a shutting down of the test station by resetting the test station for determination of failure characteristics such as the burn-in time of the IC devices.
These and other features and advantages of the present invention will be better understood by considering the following detailed description of the invention which is presented with the attached drawings.